The Anglican Communion consists of “over 70 million members” organized in “38 self-governing Churches made up of about 500 dioceses, 30,000 parishes and 64,000 individual congregations in a total of 164 countries. While the Anglican Communion does not rank among the biggest groupings of Christians, it is, after the Roman Catholic Church, arguably the most widespread”. 
In 1930 resolution 49 of the Lambeth Conference described the Anglican Communion as “a fellowship, within the one Holy Catholic and Apostolic Church, of those duly constituted dioceses, provinces or regional Churches in communion with the See of Canterbury. It consists of “particular or national Churches [who] promote within each of their territories a national expression of Christian faith, life and worship.” The resolution described a common liturgical heritage and concluded: “they are bound together not by a central legislative and executive authority, but by mutual loyalty sustained through the common counsel of the bishops in conference.”
An Episcopal Dictionary of the Church defines the Anglican Communion as follows:
“The Churches in communion with the See of Canterbury throughout the world. Member churches exercise jurisdictional independence but share a common heritage concerning Anglican identity and commitment to scripture, tradition, and reason as sources of authority. Churches in the Anglican Communion continue to reflect the balance of Protestant and Catholic principles that characterized the via media of the Elizabethan Settlement.” 
Unity and co-operation within the Communion are facilitated by a number of bodies including four which are sometimes referred to as the Instruments of Communion (see separate FAQ on this subject), namely: The Archbishop of Canterbury, the Primates’ Meeting, the Lambeth Conference and the Anglican Consultative Council.
For a complete list of the provinces of the Anglican Communion please follow this link to a listing on the Anglican Communion web site.
 2006 Church of England Year Book. London: Church House Publishing, 2005. “The Anglican Communion”, p. 337. An Episcopal Dictionary of the Church: A User-Friendly Reference for Episcopalians / Edited by Don S. Armentrout and Robert Boak Slocum. New York: Church Publishing, 1991. Vide “Anglican Communion”, p. 16.